KR101617644B1 - A method of assessing a model of a substrate, an inspection apparatus and a lithographic apparatus - Google Patents

Abstract

A method for evaluating a model of a substrate is presented. A scatterometry measurement is performed using radiation at the first wavelength. Thereafter, the wavelength of the radiation is changed and an additional scatterometry measurement is performed. If the scatterometry measurements are consistent across a range of wavelengths, the model is sufficiently accurate. However, if the scatterometry measurements change as the wavelength changes, the model of the substrate is not sufficiently accurate.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a method of evaluating a model of a substrate, an inspection apparatus and a lithography apparatus,

The present invention relates to inspection methods that are available, for example, in the manufacture of devices by lithographic techniques, and to methods of manufacturing devices using lithographic techniques.

A lithographic apparatus is a machine that applies a desired pattern onto a substrate, typically onto a target portion of the substrate. The lithographic apparatus may be used, for example, in the manufacture of integrated circuits (ICs). In that case, a patterning device, alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. comprising a portion of a die, one or several dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is typically performed through imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will comprise a network of adjacent target portions that are successively patterned. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at one time, and scanning the pattern through a radiation beam in a given direction ("scanning" -direction) Called scanner, in which each target portion is irradiated by synchronously scanning the substrate in a direction parallel (parallel to the same direction) or in a reverse-parallel direction (parallel to the opposite direction). It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern on the substrate.

In order to monitor the lithographic process, it is desirable to measure the overlay error between the parameters of the patterned substrate, for example between successive layers formed in or on the substrate. There are a variety of techniques, including scanning electron microscopy and the use of various special tools, to perform measurements of microscopic structures formed during the lithography process. One type of special inspection tool is a scatterometer in which the radiation beam is directed onto a target portion on the surface of a substrate and the characteristics of the scattered or reflected beam are measured. The characteristics of the substrate can be determined by comparing the characteristics of the beam before and after the beam is reflected or scattered by the substrate. This can be done, for example, by comparing the reflected beam with data stored in a library of known properties associated with known substrate properties. Two main forms of the scatterometer are known. A spectroscopic scatterometer directs a broadband beam of radiation onto a substrate and measures the spectrum (intensity as a function of wavelength) of the radiation scattered in a particular narrow angular range. An angularly resolved scatterometer uses a monochromatic radiation beam and measures the intensity of the scattered radiation as a function of angle.

Scatterometry uses a model of the substrate to measure the angle of the sidewall of the feature, e.g., the feature. However, if the model of the substrate is not accurate, a large error will occur in the measured features. This may occur, for example, if there are line edge roughness that was not included in the model.

It is desirable to provide a method for evaluating the accuracy of the model used in scatterometry.

According to one embodiment of the present invention, there is provided a method and apparatus for evaluating a model of a feature of a substrate, the method comprising: performing a first scatterometry measurement of a substrate using radiation having known properties; Determining a characteristic value of a feature of a substrate using a scatterometry measurement, the radiation having a first characteristic value; Performing a second scatterometry measurement using radiation having a second characteristic value; Determining a second value of a characteristic of the feature using a second scatterometry measurement; And comparing the first value and the second value of the characteristic of the feature to determine the accuracy of the model.

According to another embodiment of the present invention, there is provided a radiation projector configured to project radiation onto a substrate, the radiation having characteristics having a plurality of values; A lens of high numerical aperture; And a detector configured to detect radiation reflected from the surface of the substrate; The detector is configured to separate the detected radiation into a plurality of sub-divisions, and the radiation of each of the sub-divisions has a different value for the characteristic.

According to another aspect of the present invention, there is provided a lithographic apparatus and an inspection apparatus including an imaging Fourier transform spectrometer.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:
1 illustrates a lithographic apparatus according to one embodiment of the present invention;
Figure 2 illustrates a lithography cell or cluster according to one embodiment of the present invention;
Figure 3 illustrates a first scatterometer in accordance with an embodiment of the present invention;
Figure 4 illustrates a second scatterometer in accordance with one embodiment of the present invention;
5 is a flow diagram according to one embodiment of the present invention;
Figure 6 is a graph showing the results from a method according to one embodiment of the present invention; And
7 is a view showing a Fourier transform spectrometer according to an embodiment of the present invention.

Figure 1 schematically depicts a lithographic apparatus. The apparatus comprises an illumination system (illuminator) IL configured to condition a radiation beam B (e.g. UV radiation or DUV radiation); A patterning device support or support structure constructed to support a patterning device (e.g., mask) MA and coupled to a first positioner PM configured to accurately position the patterning device in accordance with certain parameters (e.g., For example, a mask table) (MT); A substrate table (e.g., a wafer table) configured to hold a substrate (e.g., a resist-coated wafer) W and connected to a second positioner PW configured to accurately position the substrate according to certain parameters, Wafer table) WT; And a projection system (e.g., a projection system) configured to project a pattern imparted to the radiation beam B by a patterning device MA onto a target portion C (e.g. comprising one or more dies) (E.g., a refractive projection lens system) PL.

The illumination system may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, for directing, shaping, or controlling radiation .

The patterning device support or support structure holds the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions, such as for example whether or not the patterning device is held in a vacuum environment. The patterning device support may utilize mechanical, vacuum, electrostatic, or other clamping techniques to hold the patterning device. The support structure may be, for example, a frame or a table that may be fixed or movable as required. The patterning device support can ensure that the patterning device is in a desired position, for example with respect to the projection system. Any use of the terms "reticle" or "mask" herein may be considered synonymous with the more general term "patterning device".

The term "patterning device " as used herein should be broadly interpreted as referring to any device that can be used to impart a pattern to a cross-section of a radiation beam to create a pattern in a target portion of the substrate. The pattern imparted to the radiation beam may be precisely matched to the desired pattern in the target portion of the substrate, for example when the pattern comprises phase-shifting features or so-called assist features . Generally, the pattern imparted to the radiation beam will correspond to a particular functional layer in the device to be created in the target portion, such as an integrated circuit.

The patterning device may be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in the lithographic arts and include various types of hybrid masks as well as mask types such as binary, alternating phase-shift and attenuated phase-shift types. One example of a programmable mirror array employs a matrix configuration of small mirrors, each of which can be individually tilted to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern to the radiation beam reflected by the mirror matrix.

The term "projection system " used herein should be broadly interpreted as encompassing any type of projection system, including refractive, reflective, catadioptric, catadioptric, catadioptric, But should be broadly interpreted as including any type of projection system, including magnetic, electromagnetic and electrostatic optical systems, or any combination thereof. Any use of the term "projection lens" herein may be considered as synonymous with the more general term "projection system ".

As shown herein, the apparatus is of a transmissive type (e.g. employing a transmissive mask). Alternatively, the apparatus may be of a reflective type (e.g. employing a programmable mirror array of a type as referred to above, or employing a reflective mask).

The lithographic apparatus may be of a type having two (dual stage) or more substrate tables (and / or two or more mask tables). In such "multiple stage" machines additional tables may be used in parallel, or preparatory steps may be carried out on one or more tables while one or more tables are being used for exposure.

The lithographic apparatus may also be of a type wherein all or a portion of the substrate may be covered with a liquid, e.g., water, having a relatively high refractive index, to fill the space between the projection system and the substrate. Immersion liquid may also be applied to other spaces in the lithographic apparatus, for example, between the mask and the projection system. Immersion techniques are well known in the art for increasing the numerical aperture of a projection system. The term "immersion " as used herein does not mean that a structure such as a substrate has to be immersed in liquid, but rather means that the liquid only has to lie between the projection system and the substrate during exposure.

Referring to Figure 1, the illuminator IL receives a radiation beam from a radiation source SO. For example, where the source is an excimer laser, the source and the lithographic apparatus may be separate entities. In such a case, the source is not considered to form part of the lithographic apparatus, and the radiation beam is, for example, assisted by a beam delivery system BD comprising a suitable directing mirror and / or a beam expander, Is passed from the source SO to the illuminator IL. In other cases, for example, where the source is a mercury lamp, the source may be an integral part of the lithographic apparatus. The source SO and the illuminator IL may be referred to as a radiation system together with a beam delivery system BD if necessary.

The illuminator IL may comprise an adjuster AD for adjusting the angular intensity distribution of the radiation beam. Generally, at least the outer and / or inner radial extent (commonly referred to as -outer and -inner, respectively) of the intensity distribution in the pupil plane of the illuminator can be adjusted. In addition, the illuminator IL may include various other components, such as an integrator IN and a condenser CO. The illuminator may be used to condition the radiation beam to have a desired uniformity and intensity distribution in the cross section of the radiation beam.

The radiation beam B is incident on a patterning device (e.g., mask) MA, which is held on a patterning device support (e.g., mask table) MT, and is patterned by a patterning device. Having traversed the patterning device (e.g. mask) MA, the radiation beam B passes through the projection system PL, which is directed onto the target portion C of the substrate W Focus. With the aid of the second positioner PW and the position sensor IF (e.g. interferometric device, linear encoder, 2-D encoder or capacitive sensor), the substrate table WT is moved, for example, B to position different target portions C in the path of the target portion C. Similarly, the first positioner PM and another position sensor (not explicitly depicted in FIG. 1) may be configured to detect the position of the radiation source, e.g., after mechanical retrieval from a mask library, May be used to accurately position the patterning device (e.g., mask) MA with respect to the path of beam B. [ In general, the movement of the patterning device support (e.g. mask table) MT may be accomplished using a combination of a long-stroke module and a short-stroke module, , Which forms part of the first positioner PM. Similarly, movement of the substrate table WT may be realized using a long-stroke module and a short-stroke module, which form a part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the patterning device support (e.g. mask table) MT may be connected or fixed only to the short-stroke actuators. The patterning device (e.g. mask) MA and substrate W may be aligned using mask alignment marks M1 and M2 and substrate alignment marks P1 and P2. Although the illustrated substrate alignment marks occupy dedicated target portions, they may be located in spaces between target portions (these are known as scribe-lane alignment marks). Similarly, in situations where more than one die is provided on the mask MA, the mask alignment marks may be located between the dies.

The depicted apparatus may be used in at least one of the following modes:

1. In step mode, the patterning device support (e.g. mask table) MT and the substrate table WT are kept essentially stationary while the entire pattern imparted to the radiation beam is held at the target portion C at one time, (I. E., A single static exposure). ≪ / RTI > The substrate table WT is then shifted in the X and / or Y direction so that a different target portion C can be exposed. In step mode, the maximum size of the exposure field limits the size of the target portion C imaged during a single static exposure.

2. In scan mode, the patterning device support (e.g. mask table) MT and the substrate table WT are scanned synchronously while a pattern imparted to the radiation beam is projected onto a target portion C A single dynamic exposure]. The speed and direction of the substrate table WT with respect to the patterning device support (e.g. mask table) MT may be determined by the magnification and image reversal characteristics of the projection system PL. In scan mode, the maximum size of the exposure field limits the width (in the non-scanning direction) of the target portion during a single dynamic exposure, while the length of the scanning operation determines the height of the target portion (in the scanning direction).

3. In another mode, the patterning device support (e.g., mask table) MT is kept essentially stationary holding a programmable patterning device so that the pattern imparted to the radiation beam is directed to the target portion C, The substrate table WT is moved or scanned while being projected onto the substrate table WT. In this mode, a pulsed radiation source is generally employed, and the programmable patterning device is updated as needed after each movement of the substrate table WT, or between successive radiation pulses during a scan. This mode of operation can be readily applied to maskless lithography using a programmable patterning device, such as a programmable mirror array of a type as referred to above.

Combinations and / or variations on the above described modes of use, or entirely different modes of use, may also be employed.

As shown in Figure 2, the lithographic apparatus LA sometimes forms part of a lithography cell LC, also referred to as a lithocell or a cluster, which is pre-exposed and post- post-exposure) processes. Typically, they include a spin coater (SC) for depositing resist layers, a developer (DE) for developing exposed resist, a chill plate (CH) and a bake plate (BK) do. The substrate handler or robot RO picks up the substrates from the input / output ports I / O1, I / O2, moves the substrates between different processing devices, and loads the substrates into the loading bay of the lithographic apparatus : LB). Often these devices, collectively referred to as tracks, are under the control of a track control unit (TCU), which is itself controlled by a supervisory control system (SCS) that controls the lithographic apparatus through a lithographic control unit (LACU). Thus, different devices can be operated to maximize throughput and processing efficiency.

In order for the substrates exposed by the lithographic apparatus to be correctly and consistently exposed, it is desirable to inspect the exposed substrates to measure properties such as overlay error, line thickness, critical dimension (CD), etc. between subsequent layers. If an error is detected, adjustments can be made to the exposure of subsequent substrates, particularly if the inspection can be done quickly enough so that another substrate of the same batch is still exposed. In addition, already exposed substrates can be stripped to improve yields, or to be reworked, or to avoid performing exposure on a substrate known to be defective. If only some target portions of the substrate are defective, another exposure may be performed on only good target portions.

The inspection apparatus is used to determine the characteristics of the substrate, and in particular is used to determine how the characteristics of different substrates or different layers of the same substrate vary from layer to layer. The inspection apparatus may be integrated into the lithographic apparatus LA or the lithocell LC, or it may be a stand-alone device. To enable the quickest measurements, the inspection apparatus preferably measures the properties in the exposed resist layer immediately after exposure. However, the latent image in the resist has very low contrast - there is only a small difference in the refractive index between the portion of the resist exposed to radiation and the portion of unexposed resist - But does not have sufficient sensitivity to perform useful measurements. Therefore, the measurements are typically the first step performed on the exposed substrate and may be performed after the post-exposure bake step (PEB), which increases the contrast between the exposed and unexposed portions of the resist. At this stage, the image in the resist may be referred to as semi-latent. It is also possible to perform measurements of the developed resist image, where one of the exposed or unexposed portions of the resist has been removed, or it can be performed after a pattern transfer step such as etching. The latter possibility limits the possibility of reprocessing the defective substrate, but it can still provide useful information.

Figure 3 shows a scatterometer (SMl) that may be used in an embodiment of the present invention. Which includes a broadband (white light) radiation projector 2 for projecting radiation onto a substrate W. The reflected radiation is passed to a spectrometer detector 4 which measures the spectrum 10 of the specular reflected radiation (i.e. intensity (I) as a function of wavelength?). From this data, the profile or structure generated by the detected spectrum can be analyzed by, for example, Rigorous Coupled Wave Analysis (RCWA) and non-linear regression, or by simulations as shown at the bottom of FIG. Lt; / RTI > can be reconstructed by the processing unit (PU) by comparing it with a library of spectra. In general, the general form of the structure is known for reconstruction and some parameters are assumed from the knowledge of the process in which the structure was made, leaving only some parameters of the structure to be determined from the scatterometry data. Such a scatterometer may be configured as a vertical-incidence scatterometer or an incline-incidence scatterometer.

Another scatterometer SM2 that may be used with an embodiment of the present invention is shown in FIG. In this device, the radiation emitted by the radiation source 2 is focused through the interference filter 13 and the polarizer 17 using the lens system 12, and the partially reflected surface 16 , And is focused onto the substrate W through a microscope objective lens 15 having a high numerical aperture (NA), preferably greater than or equal to 0.9 and more preferably greater than or equal to 0.95. The immersion scatterometer may even have a lens with a numerical aperture greater than one. The reflected radiation is then transmitted to the detector 18 through the partially reflective surface 16 so that a scatter spectrum is detected. The detector may be located in a back-projected pupil plane 11 that is at the focal length of the lens 15, but instead the pupil plane may be located on the detector surface using an auxiliary optics (not shown) Or may be re-imaged onto the image. The pupil plane is a plane in which the radial position of the radiation defines the angle of incidence and the angular position defines the azimuth angle of the radiation. The detector is preferably a two-dimensional detector so that the two-dimensional angular scattering spectrum of the substrate target 30 can be measured. The detector 18 may be, for example, an array of CCD or CMOS sensors, and may use an integration time of, for example, 40 milliseconds per frame.

For example, a reference beam is often used to measure the intensity of incident radiation. To this end, when the radiation beam is incident on the beam splitter 16, a part thereof is transmitted as a reference beam toward the reference mirror 14 through the beam splitter. The reference beam is then projected onto a different part of the same detector 18.

A set of interference filters 13 may be used to select wavelengths in the range of, for example, 405 to 790 nm, or much lower such as 200 to 300 nm. The interference filter may be tunable rather than including a set of different filters. Instead of interference filters, a grating can be used.

The detector 18 can measure the intensity of scattered radiation or light in a short wavelength (or narrow wavelength range), separate intensity at multiple wavelengths, or integrated intensity over a wavelength range. The detector can also measure transverse magnetic-polarization and transverse electric-intensity of polarized radiation or light, and / or phase difference between transverse magnetic-polarized and transverse electro-polarized radiation or light.

A broadband radiation or light source (i. E., A broad range of radiation frequencies or wavelengths - and hence a wide range of radiation or light sources of colors), which provides a broad etendue to permit mixing of multiple wavelengths . The plurality of wavelengths in the broadband preferably have a bandwidth of delta lambda and an interval of at least 2 delta lambda (i.e., twice the bandwidth). Several "sources" of radiation can be different parts of an extended radiation source that have been split using a fiber bundle. In this way, angle resolved scatter spectra can be measured in parallel at multiple wavelengths. A 3-D spectrum (wavelength and two different angles) containing more information than the 2-D spectrum can be measured. This allows more information to be measured that increases the metrology process robustness. This is described in more detail in EP 1,628,164 A.

The target 30 on the substrate W may be a lattice printed after the development such that the bars are formed into solid line resist lines. Alternatively, the bar can be etched into the substrate. This pattern may be sensitive to chromatic aberrations in the lithographic projection apparatus, particularly in the projection system PL, and the presence of such aberrations and the illumination symmetry will manifest itself in variations in the printed grating. Thus, scatterometry data of the printed grid is used to reconstruct the grids. From the information of the printing step and / or other scatterometry processes, parameters of the grating, such as line width and shape, can be entered into the reconstruction process performed by the processing unit (PU).

One embodiment of the present invention is used to evaluate a model of a feature on a substrate, and Figure 5 illustrates the procedures associated with an embodiment of the present invention. In procedure S1, a scatterometry measurement of the feature is performed using the substrate to be evaluated and using radiation of a known characteristic. The measurement is then used in step S2 to determine a particular characteristic of the feature of the substrate, for example a first value for the sidewall angle. After the wavelength of the radiation is changed in step S3, a second scatterometry measurement of the same feature is performed in step S4. A second value of a specific characteristic of the feature of the substrate is then determined in procedure S5. These two values of the characteristics of the feature can be compared in procedure S6. If the values are similar, it indicates that the model is correct. However, if the values are different, this may indicate that the model is not accurate. In one embodiment, it is determined if the second value of the characteristic of the feature is within a predetermined range of the first value. The predetermined range may be a proportion of the first value.

It is also possible to use residuals instead of values for a particular characteristic of the feature to evaluate the model. The residual is the difference between the angularly resolved spectrum in the pupil plane resulting from the measured structure or profile and the angularly resolved spectrum in the pupil plane resulting from the reconstructed structure or profile. A first scatterometry measurement is performed to determine a first residual. A second scatterometry measurement is performed (after the first measurement or in parallel with the first measurement) to determine the second residual. Thereafter, the first and second residuals are compared. If the residuals are similar, this indicates that the model is correct. If the residuals are different, this may indicate that the model is not accurate. Instead of residuals, goodness of fit can be used to evaluate the quality of the model, which is determined by the measured pupil plane (i.e., the measured angular resolved spectrum) and the calculated pupil plane (i.e., the reconstructed profile (The angular-resolved spectra generated from the angular-resolved spectra).

As shown in Fig. 5, the characteristics of the radiation can be changed repeatedly, and repeated measurements can be performed. As more measurements are performed, it will be easier to determine if the model is correct. Figure 6 shows the sidewall error (SWA-err) measured and determined at a plurality of wavelengths. These results were obtained by using a dense resist lattice with a pitch of 140 nm and a critical dimension of 55 nm. As can be seen, there is a large variation in sidewall error, indicating that the model is not very accurate.

In response to this determination that the model is not accurate, the model may include additional features or may be modified to adjust the current features, e.g., line edge roughness or top or bottom rounding. Therefore, embodiments of the invention enable the accuracy of the model to be evaluated.

This method can be used to evaluate whether the appropriate number of parameters are used in the model. For example, a model using as few parameters as possible can be used. If scatterometry measurements are performed at various wavelengths and the results match over a range of wavelengths, then the number of parameters used is sufficient. However, if the results vary over a range of wavelengths, additional parameters must be added until the results match over a range of wavelengths. This process can be repeated for each substrate, or alternatively, only once per batch of substrates.

While the foregoing embodiments illustrate the adjustment of the wavelength of the radiation, other characteristics of the radiation may be adjusted. For example, this is the angle of incidence, polarization or illumination mode (TE or TM) onto the substrate.

The wavelength of the radiation can be adjusted using conventional methods such as an interference filter, an acousto optical tunable filter in combination with a xenon lamp, or a supercontinuum laser. Alternatively, multiple radiation sources, each having a different wavelength, may be used. The different wavelengths of radiation can be measured sequentially or simultaneously using, for example, an imaging spectrometer. For example, a color CCD can be used to measure intensities at three different wavelengths for three color sources. The imaging spectrometer can be properly positioned within the detection branch of the apparatus.

An alternative method of achieving multiple wavelengths is to use a Fourier transform spectrometer. A Fourier transform spectrometer is shown in Fig. In this spectrometer, a beam is divided into two beams by a beam splitter 46. [ The first beam is reflected by the fixed position mirror 48 and the second beam is reflected by the moving mirror 49. Thereafter, the two beams are recombined by a beam splitter. The two beams interfere, and the interference depends on the optical delay and thus the path difference between the two beams. The intensity is then measured at the moving mirrors at a plurality of positions, and the spectrum is determined. In order to determine the exact spectrum, hundreds of intensities have to be measured: the more the measured intensity, the more accurate the spectrum. The spectrum is then subjected to a Fourier transform to obtain a measurement for each wavelength, and the relevant parameters can be determined. Such a Fourier transform spectrometer should be used, for example, with a white radiation or light source that generates a number of different wavelengths of radiation. The Fourier transform spectrometer can be placed in the lamp house of the spectrometer, or alternatively, in the front, or form part of the detector 18.

In one embodiment, the detector is configured to separate the detected radiation into a plurality of subdivided-portions, and the radiation of each of the subdivided-portions has a different value for the characteristics. The inspection apparatus may also include an imaging spectrometer configured to separate the detected radiation into a plurality of subdivision-portions, wherein the radiation of each subdivision-portion has a different value for the property.

Although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, the lithographic apparatus described herein may have other applications, such as the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, Display (LCD), thin-film magnetic heads, and the like. Those skilled in the art will recognize that any use of the terms "wafer" or "die" herein may be considered as synonymous with the more general terms "substrate" or "target portion", respectively, in connection with this alternative application I will understand. The substrate referred to herein can be processed before and after exposure, for example in a track (typically a tool that applies a resist layer to a substrate and develops the exposed resist), a metrology tool, and / or an inspection tool. Where applicable, the description herein may be applied to such substrate processing tools and other substrate processing tools. Further, the substrate may be processed more than once, for example in order to create a multi-layer IC, so that the term substrate used herein may also refer to a substrate that already contains multiple processed layers.

While specific reference may have been made above to the use of embodiments of the invention in connection with optical lithography, it is to be understood that the invention may be used in other applications, for example imprint lithography, and is not limited to optical lithography, I will understand. In imprint lithography, topography in a patterning device defines a pattern created on a substrate. The topography of the patterning device can be pressed into the resist layer supplied to the substrate on which the resist is cured by applying electromagnetic radiation, heat, pressure, or a combination thereof. The patterning device is moved from the resist leaving a pattern therein after the resist is cured.

The terms "radiation" and "beam" used herein encompass all types of electromagnetic radiation, including ultraviolet (UV) radiation (e.g. having a wavelength of, for example, 365, 355, 248, 193, 157 or 126 nm, Extreme ultra-violet (EUV) radiation (having a wavelength in the range of 5-20 nm), as well as particle beams, such as ion beams or electron beams.

The term "lens ", as the context allows, may refer to any one or combination of various types of optical components, including refractive, reflective, magnetic, electromagnetic and electrostatic optical components.

While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. For example, the invention may take the form of a computer program comprising one or more sequences of machine-readable instructions embodying a method as described above, or a data storage medium (e.g., semiconductor memory, magnetic storage, Or an optical disk).

The above description is intended to be illustrative, not limiting. Accordingly, those skilled in the art will appreciate that modifications may be made to the invention as described without departing from the scope of the claims set forth below.

Claims (21)

A method for evaluating a model of a feature of a substrate comprising:
Performing a first scatterometry measurement of the substrate using radiation having known properties, the radiation having a first characteristic value;
Determining a first value or a first residual of a feature of a feature of the substrate using the first scatterometry measurement;
Performing a second scatterometry measurement using the radiation having a second characteristic value;
Using the second scatterometry measurement to determine a second value or a second residual of a characteristic of the feature; And
Comparing the first value and the second value of the characteristic of the feature or the first residual and the second residual to determine the accuracy of the model;
/ RTI > The method according to claim 1,
Further comprising changing a characteristic of the radiation to a third value. 3. The method according to claim 1 or 2,
Performing a third scatterometry measurement using the radiation having a third characteristic value; And
Determining a third value of a property of the feature using the third scatterometry measurement;
Wherein the comparing step compares the first value, the second value, and the third value of the characteristics of the feature. The method of claim 3,
Further comprising changing a characteristic of the radiation to a fourth value. The method according to claim 1,
Wherein the radiation characteristic to be changed is a wavelength of the radiation. The method according to claim 1,
Wherein the radiation characteristic to be changed is the polarization of the radiation. The method according to claim 1,
Wherein the radiation characteristic to be changed is an incident angle onto the substrate. The method according to claim 1,
Wherein the radiation characteristic to be changed is the illumination mode of the radiation. The method according to claim 1,
Wherein the comparing comprises determining whether the second value of the characteristic of the feature is within a predetermined range of the first value. delete delete delete delete delete delete delete delete delete delete delete delete

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